working with images (PIL ?)

[Poppy]

I need to write a program to examine images (JPG) and determine how much 
area is whitespace. We need to throw a returned image out if too much of it 
is whitespace from the dataset we're working with. I've been examining the 
Python Image Library and can not determine if it offers the needed 
functionality. Does anyone have suggestions of other image libraries I 
should be looking at it, or if PIL can do what I need?